The present invention relates to apparatus and methods for fluid jet printing and particularly relates to apparatus and methods for using multiple fluid jet printing heads in a fluid jet printing line wherein each fluid jet printing head may apply a different color, dye, chemical, etc. to a common substrate, preferably a textile fabric, passing serially through each fluid jet printing station.
In a conventional fluid jet printing device, a linear array of fluid jet orifices are formed in a substrate from which filaments of fluid issue to form a plurality of droplet streams for deposition on a substrate. Individually-controllable electrostatic charging electrodes are disposed downstream of the orifice plate along a "drop formation" zone. In accordance with known principles of electrostatic conduction, these fluid filaments are provided an electrical charge opposite in polarity and related in magnitude to the electrical charge of the charging electrode. When the droplets separate from the filaments, the induced electrostatic charge is trapped on and in the droplets. The charged droplets then pass through a subsequent electrostatic field and are thereby deflected from a straight downward path toward a catcher structure. Uncharged droplets proceed along the straight path and are deposited upon the receiving substrate.
When providing a fluid jet printing device in a fabrication line to create multi-color patterns on textile substrates, a number of complications and practical problems arise. For example, when running a textile substrate sequentially through a plurality of fluid jet printing devices, it is highly desirable to locate the individual printing heads as close to one another as possible. Because textile fabrics have a width on the order of 1.8 meters, however, close spacing of the multiple fluid jet printing heads prevents access to the mid-portions of the heads. Thus, servicing one of the fluid jet printing heads intermediate the multiple heads along the fabrication line to correct any problems would be difficult, if not impossible. Also, servicing a particular fluid jet printing head in the line requires shutdown of the other printing heads and the substrate transport as well as moving the print head away from its print position. Moreover, apparatus ancillary to fluid jet printing startup, for example, startup catcher trays and test systems, if placed in the line with the heads, would be inconvenient to access, as well as space-consuming, possibly necessitating greater than the optimum close spacing of the heads one from the other. In short, it would be very difficult to service one or more of the printing heads while the printing heads are operating and highly undesirable to have extensive downtime on the printing line for purposes of servicing just one of the print station heads.
Another problem extant in the processing of textile substrates with pattern-generating fluid jet printing heads arises from the need to locate the catcher assembly of the fluid jet apparatus as close to the substrate as possible. It will be appreciated that the distance between the orifice plate and the substrate is a free-fall region in which the droplets which eventually form the image on the substrate pass uncontrolled. This distance must be maintained as small as possible to preclude introduction of trajectory-altering air currents or the like and to minimize the effect of any angular deviation of the downward path of a droplet. However, long runs of textile fabrics necessarily entail piecing fabric together at seams transverse to the direction of the run. These seams may be too thick to pass between the lower edge of the catcher and the transport belt carrying the fabric, resulting in a collision between the seam and the catcher.
The present invention integrates a solution to both of these problems in the provision of a novel and unique fluid jet printing head assembly for use in a textile fabric fabrication line. The present invention therefore provides a printing head which constitutes a transportable modular sub-system movable between a print station and a make-ready station removed from the print station and at which print station the print head can be started up, debugged and prepared for use and corrected for any improper functioning. The print head can then be moved from the make-ready station while in a running "full-catch" mode into the printing line with the assurance that, when converted in the print line from the "full-catch" mode to the full print mode, the print head will function properly and be accurately located. "Full-catch" mode means herein that all of the fluid droplets are charged by the charge electrodes and deflected by the deflection electrode such that all fluid droplets are caught by the catcher structure for recirculation and that no fluid droplets escape from being caught by the catcher structure.
More particularly, print heads can be selectively removed from and replaced in the printing line with a minimum of down-time in the line. This is accomplished by providing a base for each print head printing station in the line from which the print head may be readily removed and replaced. Each print head is provided with two sets of fluid connections, both of the quick-disconnect type, and two sets of power connections. Additionally, a number of data cable connectors affording the pattern data are provided in parallel to the charge electronics. In the event of a pattern change, for example, the print heads in the line can be converted to a "full-catch" condition and the transport stopped. The print head, which is malfunctioning or scheduled for service or in which a color change is desired, may be removed by lifting the print head from its mounting base and transported to a "clean room" for disposition on a test stand. The removed print head may then be flushed with fluid from a fluid support system. Additionally, diagnostic electronics are provided at the make-ready station which would diagnose any particular problem with such print head. A test substrate transport device is also provided on which the printing may be tested. At the make-ready station, the print head is brought up to its printing state and completely checked out as to print quality and other characteristics. All manipulations to achieve fluid jet straightness and integrity, and all electrode and catcher adjustments are performed at the make-ready station so that the print head arrives in a "ready-to-print" state while in the clean room. When the print head has been checked out and is running satisfactorily in a print mode, the print head is put into a "full-catch" mode, ready for transport back to the print line.
To transport the print head in the "full-catch" mode back to the print line, a movable transport, i.e., a crane carrying a recirculating fluid system and a power supply lifts and transports the print head into the print line while the print head is running in its "full-catch" mode. More particularly, dual sets of fluid and electronic connections are provided on the print head whereby fluid and power connections carried by the crane can be connected to the print head prior to disconnecting the fluid and power connections provided the print head in the ready-station. Additionally, the fluid and power connections used at the print station are disconnected from the print head only after the fluid and power connections carried by the crane are connected to the print head. Thus, the print head is moved from the ready-station to the print station in a full running, "full-catch" state. When in the print line, the print and flush fluids are mixed and diverted to waste before converting the print head from the "full-catch" mode to a full print mode. The entire print line may then be restarted and printing resumed by converting all print heads from the "full-catch" mode to their running mode.
It will thus be appreciated that should a malfunction occur in one or more of the print heads during printing, the line can be stopped and the malfunctioning print head removed from the line. A properly functioning print head can then replace the malfunctioning print head and the line restarted. In this manner, only minimal downtime is required and considerable savings in time are effected inasmuch as the malfunctioning print head can then be completely serviced at the make-ready station and restarted. Such servicing and restarting may take considerable effort and time and consequently the system of the present invention enables continued production of the textile fabric during such servicing. It will be appreciated, however, that a replacement fluid jet printing device may not be readily available to replace a malfunctioning device. Should this occur, the present invention still minimizes downtime by enabling quick service on the malfunctioning device in the clean room and quick and convenient startup once service is completed whereby the serviced device can be returned to the line in running condition.
The mounting between the print head and the base is provided to ensure repeatable high accuracy location of each print head in the line. That is, each replacement print head exactly replicates in location the location of the print head it replaces. This ensures repeatable and precisely located patterns printed on the substrate inasmuch as each print head cooperates with every other print head in the line to achieve certain patterns and configurations in the substrate. Such mounting constitutes a three-point mounting. The three-point mounting additionally accommodates expansion and contraction of the structure due to thermal changes.
Integrated within each print head is a mounting for the distribution bar which carries the orifice plate, charge and deflection electrodes and catcher structure which enables the bar to be raised and lowered relative to the print head and, hence, relative to the substrate transport. This enables a thickened portion, i.e., a seam across the width of the textile fabric, to pass between the transport and the catcher structure without jamming. To accomplish this, a detector, in advance of the print heads, senses the presence of a seam and provides a signal in response thereto. Fluid actuators, e.g., air cylinders, on the individual print heads are responsive to the signal and, in conjunction with a cam and cam follower arrangement, raise the print distribution bar and, hence, the catcher structure, relative to the transport at the time the seam passes below the orifice plate associated with that print head. Preferably, the distance between the orifice plate and the printing substrate surface is maintained substantially constant, while the distance between the catcher structure and the transport is enlarged to accommodate the increased thickness of the textile fabric at the seam. Once the seam has passed a particular print head, the fluid actuator and associated mechanical arrangement lower the distribution bar back to its predetermined elevation to provide the desired minimum distance between the orifice plate and the fabric, while simultaneously enabling the fabric to pass between the transport and the catcher structure.
The mounting between the print bar and the head constitutes a three-point mounting which likewise assures highly accurate and repeatable placement of the distribution bar relative to the head and substrate. Thus, accurate patterns of high resolution may be maintained in the production line notwithstanding the replacement of heads in the line, replacement of distribution bars relative to the heads and the accommodation provided for varying degrees of thickness of the substrate.
Accordingly, in accordance with one aspect of the present invention, there is provided fluid jet printing apparatus for printing on a substrate comprising a fluid jet printing head for disposition above a substrate, a print bar carried by the head including an orifice plate for flowing fluid through the orifices of the plate for deposition on the substrate, and means carried by the head mounting the print bar for movement relative to the head.
In accordance with another aspect of the present invention, there is provided a fluid jet printing apparatus for printing on a substrate, comprising a base, a fluid jet printing head including a distribution bar carrying an orifice plate, electrodes for charging and deflecting charged droplets formed by filaments of fluid flowing from the orifice plate, a catcher structure for catching deflected droplets, and electronic circuitry for charging the electrodes. A transport is provided for carrying the substrate past the orifice plate for receiving uncharged droplets from the orifice plate. Means are also carried by the base for releasably mounting the head for movement between an operative position with the orifice plate in opposition to the substrate carried by the transport and a position removed from the base. Preferably, the head is removed to a make-ready or clean room for servicing.
In a further aspect of the present invention, there is provided a fluid jet printing apparatus for printing on a substrate comprising a base, a fluid jet printing head carried by the base, the printing head carrying a print bar including an orifice plate in opposition to the substrate carried by the base, a fluid distribution bar for flowing fluid through the orifices of the orifice plate, electrodes for charging and deflecting charged droplets formed by filaments of fluid flowing from the orifice plate, a catcher structure for catching deflected droplets and electronic circuitry for charging the electrodes. Means are also provided for raising the print bar relative to the base.
A still further aspect of the present invention provides a fluid jet printing line having a plurality of fluid jet printing devices arranged serially for printing sequentially on a substrate passing along the printing line, a method of disposing a fluid jet printing device in the line comprising the steps of transporting the fluid jet printing device to the line for disposition in the line, operating the fluid jet printing device during transport to the line in a "full-catch" mode, and once disposed in the line, changing the fluid jet printing device from a "full-catch" mode to a full print mode.
An even further aspect of the present invention provides a method of operating a fluid jet printing line having a plurality of fluid jet printing devices arranged serially for printing sequentially on a substrate passing along a printing line comprising the steps of removing one of the fluid jet printing devices from the line, replacing the removed fluid jet printing device in the printing line with a replacement fluid jet printing device and operating the replacement fluid jet printing device in a "full-catch" mode as the latter device is being placed in the fluid jet printing line.
In a still further aspect of the present invention there is provided a method for accommodating an increased thickness portion of a substrate on a substrate transport as the substrate passes the orifice plate of a fluid jet printing device comprising the steps of sensing the increased thickness portion of the substrate prior to passing the orifice plate and providing a signal in response thereto and increasing the distance between the substrate transport and the orifice plate in response to the signal as the increased thickness portion of the substrate passes below the orifice plate.
Accordingly, it is a primary object of the present invention to provide novel and improved apparatus and methods for generating a pattern on a textile fabric in a textile fabrication line wherein fluid jet printing devices are arranged serially and comprise modular sub-systems which are transportable for removal from the print line and replacement by running fluid jet printing heads whereby minimum downtime in the production line is achieved.
It is another object of the present invention to provide novel and improved methods for fluid jet printing wherein the fluid jet print bar may be momentarily raised relative to the fabric transport to accommodate an increased thickness portion of a fabric, for example, at a seam, as the fabric passes below multiple fluid jet printing heads in a textile fabric production line.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.